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  • A generic C++ library that provides QtConcurrent functionality?

    - by Lucas
    QtConcurrent is awesome. I'll let the Qt docs speak for themselves: QtConcurrent includes functional programming style APIs for parallel list processing, including a MapReduce and FilterReduce implementation for shared-memory (non-distributed) systems, and classes for managing asynchronous computations in GUI applications. For instance, you give QtConcurrent::map() an iterable sequence and a function that accepts items of the type stored in the sequence, and that function is applied to all the items in the collection. This is done in a multi-threaded manner, with a thread pool equal to the number of logical CPU's on the system. There are plenty of other function in QtConcurrent, like filter(), filteredReduced() etc. The standard CompSci map/reduce functions and the like. I'm totally in love with this, but I'm starting work on an OSS project that will not be using the Qt framework. It's a library, and I don't want to force others to depend on such a large framework like Qt. I'm trying to keep external dependencies to a minimum (it's the decent thing to do). I'm looking for a generic C++ framework that provides me with the same/similar high-level primitives that QtConcurrent does. AFAIK boost has nothing like this (I may be wrong though). boost::thread is very low-level compared to what I'm looking for. I know C# has something very similar with their Parallel Extensions so I know this isn't a Qt-only idea. What do you suggest I use?

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  • Thread-safe blocking queue implementation on .NET

    - by Shrike
    Hello. I'm looking for an implementation of thread-safe blocking queue for .NET. By "thread-safe blocking queue" I mean: - thread-safe access to a queue where Dequeue method call blocks a thread untill other thread puts (Enqueue) some value. By the moment I'v found this one: http://www.eggheadcafe.com/articles/20060414.asp (But it's for .NET 1.1). Could someone comment/criticize correctness of this implementation. Or suggest some another one. Thanks in advance.

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  • Perl TCP Server handling multiple Client connections

    - by Matt
    I'll preface this by saying I have minimal experience with both Perl and Socket programming, so I appreciate any help I can get. I have a TCP Server which needs to handle multiple Client connections simultaneously and be able to receive data from any one of the Clients at any time and also be able to send data back to the Clients based on information it's received. For example, Client1 and Client2 connect to my Server. Client2 sends "Ready", the server interprets that and sends "Go" to Client1. The following is what I have written so far: my $sock = new IO::Socket::INET { LocalHost => $host, // defined earlier in code LocalPort => $port, // defined earlier in code Proto => 'tcp', Listen => SOMAXCONN, Reuse => 1, }; die "Could not create socket $!\n" unless $sock; while ( my ($new_sock,$c_addr) = $sock->accept() ) { my ($client_port, $c_ip) = sockaddr_in($c_addr); my $client_ipnum = inet_ntoa($c_ip); my $client_host = ""; my @threads; print "got a connection from $client_host", "[$client_ipnum]\n"; my $command; my $data; while ($data = <$new_sock>) { push @threads, async \&Execute, $data; } } sub Execute { my ($command) = @_; // if($command) = "test" { // send "go" to socket1 print "Executing command: $command\n"; system($command); } I know both of my while loops will be blocking and I need a way to implement my accept command as a thread, but I'm not sure the proper way of writing it.

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  • Multiple instances of the same Async task (Windows Phone)

    - by Bart Teunissen
    After googeling for ages, and reading some stuff about async task in books. I made a my first program with an async task in it. Only to find out, that i can only start one task. I want to run the task more then once. This is where i found out that that doesn't seem to work. to be a little bit clearer, here are some parts of my code: InitFunction(var); This is the Task itself public async Task InitFunction(string var) { _VarHandle = await _AdsClient.GetSymhandleByNameAsync(var); _Data = await _AdsClient.ReadAsync<T>(_VarHandle); _AdsClient.AddNotificationAsync<T>(_VarHandle, AdsTransmissionMode.OnChange, 1000, this); } This works like a charm when i execute the task only once.. But is there a possibility to run it multiple times. Something like this? InitFunction(var1); InitFunction(var2); InitFunction(var3); Because if i do this now (multiple tasks at once), the task it wants to start is still running, and it throws an exeption. if someone could help me with this, that would be awesome! ~ Bart

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  • OGNL thread safety

    - by Dewfy
    I'm going to reuse OGNL library out of Struts2 scope. I have rather large set of formulas, that is why I would like to precompile all of them: Ognl.parseExpression(expressionString); But I'm not sure if precompiled expression can be used in multi-thread environment. Does anybody knows if it can be used?

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  • How do I know if a boost thread is done ?

    - by jules
    I am using boost::thread to process messages in a queue. When a first message comes I start a message processing thread. When a second message comes I check if the message processing thread is done. if it is done I start a new one if it is not done I don nothing. How do I know if the thread is done ? I tried with joinable() but it is not working, as when the thread is done, it is still joinable. I also tried to interrupt the process at once, and add an interruption point at the end of my thread, but it did not work. Thanks

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  • Why wait should always be in synchronized block

    - by diy
    Hi gents, We all know that in order to invoke Object.wait() , this call must be placed in synchronized block,otherwise,IllegalMonitorStateException is thrown.But what's the reason for making this restriction?I know that wait() releases the monitor, but why do we need to explicitly acquire the monitor by making particular block synchronized and then release the monitor by calling wait() ? What is the potential damage if it was possible to invoke wait() outside synch block, retaining it's semantics - suspending the caller thread ? Thanks in advance

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  • Java Thread - Synchronization issue

    - by Yatendra Goel
    From Sun's tutorial: Synchronized methods enable a simple strategy for preventing thread interference and memory consistency errors: if an object is visible to more than one thread, all reads or writes to that object's variables are done through synchronized methods. (An important exception: final fields, which cannot be modified after the object is constructed, can be safely read through non-synchronized methods, once the object is constructed) This strategy is effective, but can present problems with liveness, as we'll see later in this lesson. Q1. Is the above statements mean that if an object of a class is going to be shared among multiple threads, then all instance methods of that class (except getters of final fields) should be made synchronized, since instance methods process instance variables?

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  • Where to begin with multi-threaded programming with c++?

    - by zoke
    I'm trying to implement my own IRC client as a personal proejct and I realized I needed a way to read and write from the socket at the same time. I realized I could have a reading thread which reads from the socket in the background and puts data in a queue and I could have another thread which writes data from a queue to the socket. However I have no idea on how to start with multithreaded programing or how to do it with c++. Where do I go from here?

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  • Multiple things at once (Threads?)

    - by Jonathan
    All, What is a really simple way of having a program do more than one thing at once, even if the computer does not necessarily have multiple 'cores'. Can I do this by creating more than one Thread? My goal is to be able to have two computers networked (through Sockets) to respond to each-other's requests, while my program will at the same time be able to be managing a UI. I want the server to potentially handle more than one client at the same time as well. My understanding is that the communication is done with BufferedReader.readLine() and PrintWriter.println(). My problem is that I want the server to be waiting on multiple readLine() requests, and also be doing other things. How do I handle this? Many thanks, Jonathan

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  • pthread_create followed by pthread_detach still results in possibly lost error in Valgrind.

    - by alesplin
    I'm having a problem with Valgrind telling me I have some memory possible lost: ==23205== 544 bytes in 2 blocks are possibly lost in loss record 156 of 265 ==23205== at 0x6022879: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==23205== by 0x540E209: allocate_dtv (in /lib/ld-2.12.1.so) ==23205== by 0x540E91D: _dl_allocate_tls (in /lib/ld-2.12.1.so) ==23205== by 0x623068D: pthread_create@@GLIBC_2.2.5 (in /lib/libpthread-2.12.1.so) ==23205== by 0x758D66: MTPCreateThreadPool (MTP.c:290) ==23205== by 0x405787: main (MServer.c:317) The code that creates these threads (MTPCreateThreadPool) basically gets an index into a block of waiting pthread_t slots, and creates a thread with that. TI becomes a pointer to a struct that has a thread index and a pthread_t. (simplified/sanitized): for (tindex = 0; tindex < NumThreads; tindex++) { int rc; TI = &TP->ThreadInfo[tindex]; TI->ThreadID = tindex; rc = pthread_create(&TI->ThreadHandle,NULL,MTPHandleRequestsLoop,TI); /* check for non-success that I've omitted */ pthread_detach(&TI->ThreadHandle); } Then we have a function MTPDestroyThreadPool that loops through all the threads we created and cancels them (since the MTPHandleRequestsLoop doesn't exit). for (tindex = 0; tindex < NumThreads; tindex++) { pthread_cancel(TP->ThreadInfo[tindex].ThreadHandle); } I've read elsewhere (including other questions here on SO) that detaching a thread explicitly would prevent this possibly lost error, but it clearly isn't. Any thoughts?

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  • How do I wait for all other threads to finish their tasks?

    - by Mike
    I have several threads consuming tasks from a queue using something similar to the code below. The problem is that there is one type of task which cannot run while any other tasks are being processed. Here is what I have: while (true) // Threaded code { while (true) { lock(locker) { if (close_thread) return; task = GetNextTask(); // Get the next task from the queue } if (task != null) break; wh.WaitOne(); // Wait until a task is added to the queue } task.Run(); } And this is kind of what I need: while (true) { while (true) { lock(locker) { if (close_thread) return; if (disable_new_tasks) { task = null; } else { task = GetNextTask(); } } if (task != null) break; wh.WaitOne(); } if(!task.IsThreadSafe()) { // I would set this to false inside task.Run() at // the end of the non-thread safe task disable_new_tasks = true; Wait_for_all_threads_to_finish_their_current_tasks(); } task.Run(); } The problem is I don't know how to achive this without creating a mess.

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  • Millisecond-Accurate Scheduling of Future Events in C++/CLI

    - by A Grad Student at a University
    I need to create a C++/CLI mixed assembly that can schedule future calls into a native DLL with millisecond accuracy. This will, of course, mean setting a timer (what kind?) for a millisecond or three beforehand, then spinning until the moment and calling the native DLL function. Based on what I've read, I would guess that the callback that the timer calls will need to be native to make sure there are no thunks or GC to delay handling the timer callback. Will the entire thread or process need to be native and CLR-free, though, or can this be done just as accurately with #pragma unmanaged or setting one file of the assembly to compile as native? If so, how? If there is indeed no way to do this in mixed-mode C++/CLI, what would be the easiest way to set up an app/thread (ie, DLL or exe?) to handle it and to get the data back and forth between the native and managed threads/apps?

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  • Handling a Long Running jsp request on the server using Ajax and threads

    - by John Blue
    I am trying to implement a solution for a long running process on the server where it is taking about 10 min to process a pdf generation request. The browser bored/timesout at the 5 mins. I was thinking to deal with this using a Ajax and threads. I am using regular javascript for ajax. But I am stuck with it. I have reached till the point where it sends the request to the servlet and the servlet starts the thread.Please see the below code public class HelloServlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("POST request!!"); LongProcess longProcess = new LongProcess(); longProcess.setDaemon(true); longProcess.start(); request.getSession().setAttribute("longProcess", longProcess); request.getRequestDispatcher("index.jsp").forward(request, response); } } class LongProcess extends Thread { public void run() { System.out.println("Thread Started!!"); while (progress < 10) { try { sleep(2000); } catch (InterruptedException ignore) {} progress++; } } } Here is my AJax call <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html><head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>My Title</title> <script language="JavaScript" > function getXMLObject() //XML OBJECT { var xmlHttp = false; xmlHttp = new XMLHttpRequest(); //For Mozilla, Opera Browsers return xmlHttp; // Mandatory Statement returning the ajax object created } var xmlhttp = new getXMLObject(); //xmlhttp holds the ajax object function ajaxFunction() { xmlhttp.open("GET","HelloServlet" ,true); xmlhttp.onreadystatechange = handleServerResponse; xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded'); xmlhttp.send(null); } function handleServerResponse() { if (xmlhttp.readyState == 4) { if(xmlhttp.status == 200) { document.forms[0].myDiv.value = xmlhttp.responseText; setTimeout(ajaxFunction(), 2000); } else { alert("Error during AJAX call. Please try again"); } } } function openPDF() { document.forms[0].method = "POST"; document.forms[0].action = "HelloServlet"; document.forms[0].submit(); } function stopAjax(){ clearInterval(intervalID); } </script> </head> <body><form name="myForm"> <table><tr><td> <INPUT TYPE="BUTTON" NAME="Download" VALUE="Download Queue ( PDF )" onclick="openPDF();"> </td></tr> <tr><td> Current status: <div id="myDiv"></div>% </td></tr></table> </form></body></html> But I dont know how to proceed further like how will the thread communicate the browser that the process has complete and how should the ajax call me made and check the status of the request. Please let me know if I am missing some pieces. Any suggestion if helpful.

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  • throwing exception from APCProc crashes program

    - by lazy_banana
    I started to do some research on how terminate a multithreaded application properly and I found those 2 post(first, second) about how to use QueueUserAPC to signal other threads to terminate. I thought I should give it a try, and the application keeps crashing when I throw the exception from the APCProc. Code: #include <stdio.h> #include <windows.h> class ExitException { public: char *desc; DWORD exit_code; ExitException(char *desc,int exit_code): desc(desc), exit_code(exit_code) {} }; //I use this class to check if objects are deconstructed upon termination class Test { public: char *s; Test(char *s): s(s) { printf("%s ctor\n",s); } ~Test() { printf("%s dctor\n",s); } }; DWORD CALLBACK ThreadProc(void *useless) { try { Test t("thread_test"); SleepEx(INFINITE,true); return 0; } catch (ExitException &e) { printf("Thread exits\n%s %lu",e.desc,e.exit_code); return e.exit_code; } } void CALLBACK exit_apc_proc(ULONG_PTR param) { puts("In APCProc"); ExitException e("Application exit signal!",1); throw e; return; } int main() { HANDLE thread=CreateThread(NULL,0,ThreadProc,NULL,0,NULL); Sleep(1000); QueueUserAPC(exit_apc_proc,thread,0); WaitForSingleObject(thread,INFINITE); puts("main: bye"); return 0; } My question is why does this happen? I use mingw for compilation and my OS is 64bit. Can this be the reason?I read that you shouldn't call QueueApcProc from a 32bit app for a thread which runs in a 64bit process or vice versa, but this shouldn't be the case.

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  • Progressbar behaves strangely

    - by wanderameise
    I just created an application in C# that uses a thread which polls the UART for a receive event. If data is received an event is triggered in my main thread (GUI) and a progress bar is controlled via PerformStep() method (of course, I previously set the Max value accordingly). PerformStep is invoked using the following expression to handle cross threading this.Invoke((Action)delegate{progressBar2.PerformStep();}) When running this application the progressbar never hits its final value. It stops at 80%. When debugging and stopping at the line mentioned above, everything works fine using single steps. I have no idea what is going one! Start read thread on main thread: pThreadWrite = new Thread(new ThreadStart(ReadThread)); pThreadWrite.Start(); Read Thread: private void ReadThread() { while(1) { if (ReceiveEvent) { FlashProgressBar(); } } } Event that is triggered in main thread: private void FlashProgressBar() { this.Invoke((Action)delegate { progressBar2.PerformStep();}); } (It's a simplified representation of my code) It seems as if the internal progress is faster than the visual one.

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  • WM6x IMAPIAdviseSink::OnNotify threading issues

    - by violet313
    specifically WM6x, winCE5x Now my current understanding from trawling the msdn etal is that the IMAPIAdviseSink::OnNotify callback can be made from any old thread; from (ce)mapi or perhaps even from a third-party service provider. Under WM6x, i cannot seem to coax an in-thread response by invoking HrThisThreadAdviseSink, since while this function is declared in mapiutil.h, a definition appears not to exist (in cemapi.lib or wherever??) ~But i notice that all the OnNotify callbacks i receive derive from windows messages that i am receiving on my thread (=looks to me like an in-thread implementation in any case under cemapi)... So, can anyone confirm that this is infact always the case -or am i just getting lucky right now? ah, i should add that my advise source is IMAPISession::Advise erm i should also say that i might have cross-posted this on the msdn forum -but they're mostly numptys over there,,

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  • Fast way to pass a simple java object from one thread to another

    - by Adal
    I have a callback which receives an object. I make a copy of this object, and I must pass it on to another thread for further processing. It's very important for the callback to return as fast as possible. Ideally, the callback will write the copy to some sort of lock-free container. I only have the callback called from a single thread and one processing thread. I only need to pass a bunch of doubles to the other thread, and I know the maximum number of doubles (around 40). Any ideas? I'm not very familiar with Java, so I don't know the usual ways to pass stuff between threads.

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  • Repeated host lookups failing in urllib2

    - by reve_etrange
    I have code which issues many HTTP GET requests using Python's urllib2, in several threads, writing the responses into files (one per thread). During execution, it looks like many of the host lookups fail (causing a name or service unknown error, see appended error log for an example). Is this due to a flaky DNS service? Is it bad practice to rely on DNS caching, if the host name isn't changing? I.e. should a single lookup's result be passed into the urlopen? Exception in thread Thread-16: Traceback (most recent call last): File "/usr/lib/python2.6/threading.py", line 532, in __bootstrap_inner self.run() File "/home/da/local/bin/ThreadedDownloader.py", line 61, in run page = urllib2.urlopen(url) # get the page File "/usr/lib/python2.6/urllib2.py", line 126, in urlopen return _opener.open(url, data, timeout) File "/usr/lib/python2.6/urllib2.py", line 391, in open response = self._open(req, data) File "/usr/lib/python2.6/urllib2.py", line 409, in _open '_open', req) File "/usr/lib/python2.6/urllib2.py", line 369, in _call_chain result = func(*args) File "/usr/lib/python2.6/urllib2.py", line 1170, in http_open return self.do_open(httplib.HTTPConnection, req) File "/usr/lib/python2.6/urllib2.py", line 1145, in do_open raise URLError(err) URLError: <urlopen error [Errno -2] Name or service not known>

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  • How to stop Interruptible Threads in Java

    - by Dr.Lesh
    I have a Java application that I CAN'T EDIT that starts a Thread wich has this run method: public void run(){ while(true){ System.out.println("Something"); } } And at a certain moment I wanna stop it, but if I use thread.interrupt(); it won't work. If I use thread.stop(); it works, but this method is deprecated and its use is discouraged because soon it will be removed from JVM. Does anyone knows how to do it? Thank you.

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  • When Should I Use Threads?

    - by cam
    As far as I'm concerned, the ideal amount of threads is 3: one for the UI, one for CPU resources, and one for IO resources. But I'm probably wrong. I'm just getting introduced to them, but I've always used one for the UI and one for everything else. When should I use threads and how? How do I know if I should be using them?

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  • C++ thread to separate process

    - by silverbandit91
    Is there any way I can have a thread branch off into its own independent process? I know there's the CreateProcess function but as far as I can tell, you can only run external applications with it. Is what I'm asking for at all possible?

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